The goal of this project is to analyze human lymphoid cells using rapid flow cytometry for diagnostic and therapeutic applications. Membrane antigens, DNA and light scatter of cells from human B-cell lymphomas are used to measure neoplastic and non-neoplastic populations in each tumor without physical separation of cells. By comparing cellular DNA of immunoglobulin light chain-bearing neoplastic cells with that of nonneoplastic cells from the same tumor and using normal lymphoid tissues as controls, DNA changes (aneuploidy) are detected in 85% of the lymphomas. This was confirmed by comparing the DNA of non-neoplastic T cells with that of neoplastic cells from the same tumors. Ploidy ranged from near diploidy to near tetraploid levels. All lymphomas with large neoplastic S-fractions (12% or more) were histologically unfavorable lymphomas and most were hyperdiploid. Conversely, the majority of lymphomas with small S-phase fractions were diploid, near diploid or "biclonal" favorable lymphomas. Aneuploid cells were larger (higher scatter) than diploid cells in the majority of the lymphomas. Relatively high numbers of T cells were found in the B-cell lymphomas. The percentage of T cells did not correlate with tumor histology, ploidy level or size of S fraction. Flow cytometric analysis of lymphocyte surface antigens in unfractionated blood preparations using dual light scatter detectors has been successfully performed to quantitate circulating lymphocyte subtypes and to characterize the antigenic profile of leukemic cells. This is a simple analysis that may permit the rapid detection of low levels of circulating neoplastic lymphoid cells.